Choroidal melanoma is the most common primary ocular malignancy, with some 1500 new cases reported yearly in the United States. These tumors are both sight- and life-threatening. The COMS trial for medium choroidal melanomas, demonstrated that 125Iodine radioactive plaque treatment alone, without enucleation, does not increase mortality. Medium-sized choroidal melanomas can be treated and the eye and some vision preserved by application of 125Iodine brachytherapy. However, the dose distribution generated by the currently used "seeded" plaques is non-uniform and highly complex. It is extremely difficult if not impossible to accurately achieve the desired radiation dose distribution at varying points within the eye and even within the tumor. After treatment, greater than 40% of eyes have experienced significant radiation associated ocular complications. This Phase II program intends to develop an improved brachytherapy plaque for the treatment of choroidal melanoma. The source would be manufactured through a process by which the 125Iodine distribution on the surface of the plaque could be designed to provide a prescribed dose distribution. Such development would provide better dose uniformity than the current seed plaque and would permit the dose distribution to be contoured to conform to the specific tumor. Such development would also provide a measure of customization to the plaque design, providing accommodations and clearances around interferences such as the optic nerve. Additionally, such plaques would achieve a high degree of customization of the dose rate, allowing the treatment time to be specified within very narrow limits. This plaque would be thinner than the current seeded plaques, which would provide a lesser degree of discomfort to the patient. This plaque would be designed to be reusable, greatly reducing the cost for this portion of the treatment. A conformal brachytherapy plaque using 125Iodine can be an effective treatment device for this cancer.